<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <ul>
        <li>1</li>
        <li>2</li>
        <li>3</li>
    </ul>
    <script src="https://code.jquery.com/jquery-3.1.1.min.js"></script>
    <script>
        $('ul').append('<li>4</li>');
        $('<li>5</li>').appendTo('ul');
        $('ul').prepend('<li>0</li>');
        $('<li>-1</li>').prependTo('ul');
        console.log($('li:first-child').html());
        $('ul li:first-child').html('jquery修改html');
        $('ul li:nth-child(2)').text('jquery修改text');

    </script>
</body>

</html>